Additional effect of neuromuscular electrical stimulation in a conservative intervention on morphology and strength of abductor hallucis muscle and correction of hallux valgus deformity: a randomized controlled trial

Abstract

Background: In hallux valgus, morphological changes and functional weakness of intrinsic foot muscles occur, especially in the abductor hallucis muscle.

Objectives: This study aimed to investigate how a conservative treatment with the addition of neuromuscular electrical stimulation affects the volume and strength of the muscle, the correction of deformity, passive range of motion, pain, and disability.

Methods: Twenty-eight female participants (48 feet) were randomly assigned to two groups. The interventions included orthoses and exercise (Ortho) in both groups. One group received additional neuromuscular electrical stimulation of abductor hallucis muscle to activate it. Each group received the treatments for one month and was assessed two times, at baseline before starting and after one month of treatment. Mixed within-between ANOVA, analysis of covariance, and nonparametric tests were used for data analysis.

Results: The muscle volume, abduction strength, goniometric angle, and passive hallux dorsi/plantar flexion showed significant changes in both groups (p < .001). Subscales of the foot and ankle ability questionnaire, significantly changed (p ≤ .05). Pain decreased significantly in the two groups (p < .001 and p = .02). Intermetatarsal angle did not significantly differ between the two groups (p = .86, partial eta effect size = 0.001). But, the hallux valgus angle mean (on MRI) in the Ortho group was less than that of the orthoNMES group (p = .007, partial eta effect size = 0.15).

Conclusion: Both groups showed nearly identical treatment effects in the primary volume and hallux valgus correction outcome measures. In this study, adding neuromuscular electrical stimulation did not have an additional effect compared to conservative in the treatment of hallux valgus.

Trial registration number: The RCT Code is IRCT20200915048725N1.

Keywords: Hallux abductovalgus; muscle volume; neuromuscular electrical stimulation; pain; range of motion.